Casein kinase II stabilizes the activity of human topoisomerase IIalpha in a phosphorylation-independent manner.
Previous reports have indicated that topoisomerase II (topo II) co-purifies with and is a substrate for casein kinase II. We have carried out a detailed study of the effect that purified casein kinase II has on the activity of purified recombinant human topo IIalpha. Co-incubation of topo IIalpha and casein kinase II led to an apparent activation of the topo IIalpha; however, in experiments in which topo IIalpha was preincubated at 37 degrees C with or without native casein kinase II prior to assaying for decatenation activity, it emerged that the kinase was exerting its "activating" function via a decrease in the rate of topo IIalpha enzyme inactivation during the incubation period. This stabilization of topo IIalpha by casein kinase II was ATP-independent and was observed in both mutated and truncated derivatives of topo IIalpha lacking the major casein kinase II phospho-acceptor sites, indicating the lack of a requirement for phosphorylation. Consistent with a nonenzymatic role for casein kinase II, stoichiometric quantities of kinase were required for topo IIalpha stabilization. These data indicate that casein kinase II plays a significant role in regulating human topo IIalpha protein action via stabilization against thermal inactivation.
Redwood
C
C
Imperial Cancer Research Fund Laboratories, Institute of Molecular Medicine, University of Oxford, John Radcliffe Hospital, Oxford, OX3 9DS, United Kingdom.
Davies
S L
SL
Wells
N J
NJ
Fry
A M
AM
Hickson
I D
ID
D000951:Antigens, Neoplasm; D047390:Casein Kinase II; D002467:Cell Nucleus / Q000201:enzymology; D004250:DNA Topoisomerases, Type II / Q000378:metabolism*; D004268:DNA-Binding Proteins; D004795:Enzyme Stability; D006367:HeLa Cells; D006801:Humans; D007527:Isoenzymes / Q000037:antagonists & inhibitors / Q000378:metabolism*; D010766:Phosphorylation; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism*; D011994:Recombinant Proteins / Q000037:antagonists & inhibitors / Q000378:metabolism; D013379:Substrate Specificity; D059005:Topoisomerase II Inhibitors
D000951:Antigens, Neoplasm; D004268:DNA-Binding Proteins; D007527:Isoenzymes; D011994:Recombinant Proteins; D059005:Topoisomerase II Inhibitors; D047390:Casein Kinase II; D017346:Protein Serine-Threonine Kinases; D004250:DNA Topoisomerases, Type II